Silver recovery unit



Feb. 20, 1968 H. G. HARTMAN SILVER RECOVERY UNIT Filed NOV. 10, 1965HARLAN G" HARTMAN I NVENTOR.

, BKfMM @QUQBT?% ATTORNEYS United States Patent 3,369,801 SILVERRECOVERY UNIT Harlan G. Hartman, Rochester, N.Y., assignor to EastmanKodak Company, Rochester, N.Y., a corporation of New Jersey Filed Nov.10, 1965, Ser. No. 507,156 8 Claims. (Cl. 26622) ABSTRACT OF THEDISCLOSURE Apparatus for recovering silver from a silver-containingsolution, such as a photographic fixing bath, comprising a containerenclosing a fluid permeable metallic filler element composed of a metalabove silver in the electromotive force series, for example, acontinuous sheet of steel wool wound about an open core, and fluidfitting means removably attached to the container, for example, a pairof concentrically arranged pipes equipped with quick attach and releasemeans, adapted to direct the solution through the filler element,whereby the solution reacts with the metal of the filler element so thatthe silver is deposited therein.

This invention relates to a novel silver recovery unit and manner ofmaking the same. More particularly this invention relates to an improvedsilver recovery unit which is easily handled, installed and replacedthus making it particularly adapted for use in photographic processingsystems.

Numerous instances are encountered where it is desirable that certainconcentrations of materials suspended or dissolved in a fluid medium beremoved therefrom. One such instance where this is true is to be foundin the developing process normally followed in processing exposedphotographic plates or films. For example, the various silver saltsemployed in the manufacture of photographic paper and film when fixed bythe various fixatives or stop agents produces a complex silver saltwhich is dissolved or suspended in the solution. As the fixatives orstop agents become depleted it is necessary that they be replaced tokeep the fixing solution at a given strength or concentration if uniformand acceptable results are to be obtained. Often this replenishing isdone on a continuous basis by the addition of a given volume ofconcentrated solution of the fixatives or stop agents to the fixing vatswhile at the same time an equivalent volume of the spent solution iswithdrawn. If no apparatus is provided for removing the silver saltsfrom this spent solution that is being withdrawn from the vats then thesilver dissolved or suspended therein will be lost. This loss of silvercan reach sizable proportions where a large commerical developingoperation is involved.

Therefore, considerable time and expense has been expended in an effortto develop a simple, inexpensive yet highly efiicient silver recoveryunit that can be used in existing photographic processing systems.Recently this,

development effort has centered around passing the solution containingthe silver salts through various metallic elements or fillers. Themetallic filler is selected from the group of metals that is anodic tosilver so that a chemical replacement action will occur which causesprecipitation and depsition of the silver as the metallic element isdissolved. Silver recovery units of this type have been found to behighly efiicient as far as recovery is concerned. However, theygenerally are rather expensive to produce and, more importantly, hard toinstall and service on existing photographic processing systems.Furthermore, there is no convenient way of handling the silver sludgeduring shipment, following the depletion of the metallic filler element.

3,369,801 Patented Feb. 20, 1968 "ice According to this invention it hasbeen found that an effective silver recovery unit can be produced whichis compatible with existing photographic processing systems and can beincluded therein at a nominal cost. The construction of the recoveryunit is such that the metallic filler elements need never be removedfrom the housing, and no special time consuming and laborious connectingsteps are involved in coupling the unit into or removing it from aprocessing system.

Basically, the recovery unit of this invention consists of a uniquecontainer having a novel metallic filler located therein. A specialconnector is employed for rapidly connecting the recovery unit to aphotographic processing system with a minimum of effort. This connectorpermits the silver containing solution to flow completely through thefiller prior to its being sewered or returned to a fixing tank thusleaving the silver deposited as a sludge in the container.

Therefore, an object of this invention is to provide a simple,inexpensive, yet highly reliable silver recovery unit.

Another object of this invention is to provide a cartridge type silverrecovery unit that can be installed and removed from existingphotographic processing systems in a rapid, simple and inexpensivemanner.

Yet another object of this invention is to provide a cartridge typesilver recovery unit that can be handled shipped and stored without anyspecial precautionary or preparatory steps being required.

Yet still another object of this invention is to provide a silverrecovery unit having a quick detachable fluid coupling system forexpediting the changing of such units.

A further object of this invention is to provide a silver recovery unithaving a container and metallic filler element that are stored, shipped,used and returned as a single unitary body.

These and further objects and advantages of this invention will becomemore apparent upon reference to the following description, appendedclaims and drawings wherein:

FIGURE 1 is a front elevation, partly in section, showing a silverrecovery unit constructed in accordance with the present invention;

FIGURE 2 is an enlarged fragmentary view of the top of the metallicfiller element, container lid, and quick attach and release fittingfluid conductor of this invention;

FIGURE 3 is a cross-sectional view taken along line 33 of FIGURE 2showing details of the quick attach and release coupling unit; and

FIGURE 4 is a side view of a second type pressure bypass unit that canbe used for preventing dangerous zbuildups in pressure from occurringwithin the silver recovery unit.

With continued reference to the accompanying figures wherein likereference numerals designate similar parts throughout the various views,and with particular attention directed to FIGURE 1, reference numeral 10is used to designate generally a silver recovery unit constructed inaccordance with this invention. The silver recovery unit 10 consists ofthree major units, namely: 1) an outer container 12; (2) acartridge-like metallic filler element 14; and (3) a quick disconnectfluid conduit and fitting 16. The outer container or housing 12 can beconstructed of any suitable material such as metals or plastics and canbe of any size or shape that is practical for the particular use to beencountered. Normally, the only element attached to the inner wall 18 ofthe container 12 is a perforated baflle or diffusion plate 20. The outerperipheral edge 22 of the plate 20 is shown engaged against the wall 18in a fluid tight manner to assure that any flow of liquid from the area24 between the lower face of the plate and the bottom26 of the containerwill occur through the apertures 28 in the plate. However, the plate canbe loosely mounted within the container and supported on legs ratherthan attached directly to the container wall if such is desirable. Thelid or top 30 of the container can be of the removable type that is heldsecurely in place by quick releasable clamps 32 if such is desirable.However, the use of such a removable lid is not necessary nor evenparticularly desirable since the container can be made in such aninexpensive manner that it can be smelted with the filler element thuseliminating the need to ever remove or handle the filler element per se.

The metallic filler element 14 is fluid permeable and must be made froma free metal which is above silver in the electromotive series. Althoughseveral such metals are known that will perform satisfactorily, it hasbeen found that iron in the form of steel wool is best suited to thisuse. Preferably the steel WOOl is in the form of a continuous strandwhich is wound about a spool or open core 34 in a tight and continuousmanner. The use of such a continuous sheet of steel wool is advantageoussince it not only is easily applied, but its use assures that nocavities or open areas are left in the finished filler element as oftenoccurs if a loose wool is packed into a cartridge unit. Conversely, theuse of the continuous steel wool assures that no overly packed areas areformed which would unduly inhibit the flow of a solution therethrough.If desirable, the filler element may be made by assembling a number ofpreformed steel wool discs around the core as long as no voids oroverpacked areas are produced.

The spool 34 around which the steel wool is wound is important since itnot only serves as a convenient holder for the filler element, but thepassageway within the spool helps properly position the fluid fitting 16in a manner that will be more fully explained hereinafter. Lifting earsor handles 35 may be formed on the upper end of the spool for handlingor positioning the filler element within the container 12 if such isdesirable.

The diameter of the complete filler element 14 is such that it fitssnuggly into the container 12 so that no channel or passage between theinner container wall and element exists through which the silversolution can flow. Thus all fluids which leave the recovery unit willhave to flow through the fluid permeable filler element 14. The lengthof the filler element may vary depending on the quantity and silverconcentration of the fluid to be handled per unit of time, butpreferably the filler element extends from the diffusion plate 29 to apoint close to the lid 30 of the container. However, a small open area36 must be left between the lid 30 and the top of the filler element 14for permitting the silver depleted solution to enter the exit port ofthe fluid fitting 16.

The quick disconnect fluid fitting 16 used with the container 12consists of concentrically located hollow fluid conducting conduits, thefirst of which is indicated at 42. The conduit 42 has an inlet port 38at one end and is of sufiicient length so that the free end 39 thereofwill extend through most of the passageway 44 of the spool 34 wheneverthe fitting 16 is locked in place, but not through the diffusion plate20 into the open area 24 within the container 12. If the free end 39 ofthe fluid fitting 16 is permitted to project into the open area 24, orotherwise be exposed on its outer surface to the silver containingsolution, silver may deposit on the free end and prevent the easywithdrawal of the fitting. Thus the outer diameter of the hollow fluidconduit 42 is such that a snug fit is obtained between the outer wall ofthe conduit 42 and the wall of the passageway 44. Such a tight fit isalso necessary to minimize the amount of solution that flows up thepassageway and thereby avoids passing through the filler element 14. Ifnecessary, an O-ring seal 46 can be used to assure that no solution willflow between the outer wall of the conduit 42 and the wall of thepassageway 44. An inlet hose 48 is force fitted over the upper end 50 ofthe conduit 42, which may be smooth, threaded or serrated, and is heldthereon in a fluid tight manner by a suitable C-ring type clamp 52. Apressure relief valve 53 is provided in the conduit 42 for releasing anyexcess pressure that may develop within the container 12. This reliefvalve 53 is shown as being of the type employing a spring loaded poppet,but may be of any other suitable type that will open when the internalpressure within the conduit exceeds a predetermined value.

An outlet port 54 is provided for the silver removal unit 10 whichconsists primarily of a hollow L-shaped fluid conduit 56. As will beseen in FIGURE 2, one leg 58 of the L-shaped fluid conduit 56 ispositioned around and encases the inlet conduit 42 but is spacedradially therefrom by a sufficient amount so as to form a passageway 60for the upward flow of the silver depleted solution. A suitable fluidtight seal 62 is provided at the top of the leg 58 to prevent the escapeof any solution between the two conduits 42 and 56. The second leg 64 ofthe L-shaped conduit 56 is provided on its outer surface with a threadedor toothed surface 66 for receiving in afluid tight manner a flexibleoutlet hose 68. A C-ring 70 or other like clamping device is used tosecure the hose to the conduit leg 64. A pressure relief valve 71 isalso provided on the conduit 56 for releasing any pressure Within theconduit that exceeds a predetermined value.

Various other suitable types of pressure release valves and systemsbesides those shown at 53 and 71 may be used to prevent a dangerousbuild-up in operating pressure from occurring within the cartridge unit.One such pressure release system is shown in FIGURE 4 and consists of aninverted U-shaped bypass conduit 73 attached at either end to the inletport 38 and outlet port 54 by two T units 75-77, respectively. Anaperture or pressure opening 79 is provided at the top of the conduit 73so that any pressure build-up in the container 12 which is high enoughto force the solution up the conduit 73 against theforce of gravity willbe vented through the pressure opening.

A quick attach and release catch 72 is provided on the conduit 56 (seeFIGURE 2) for securing the fluid fitting 16 to the lid 30 of thecontainer 12. This catch 72 is shown for purposes of illustration inFIGURES 2 and 3 as being of the keyed type consisting of keys or lockingears 74 carried on the conduit leg 58 which are adapted to slide downmating grooves 76 into a lock channel 78 (as indicated by the brokenline in FIG- URE 3) formed in the lid 30. With the keys 74 positionedwithin the lock channel 78, the fitting 16 is locked in place byrotating either the lid or fitting 16 one-quarter turn. Any othersuitable catch could be used which permits the fitting 16 to be readilyattached and removed from the container 12 without the use of specialtools or the disconnecting of the flexible hoses 48 and 68.

The operation of the silver recovery unit may be described in thefollowing manner. A container unit 12 having a filler element 14installed therein is taken from storage and positioned in the place itis to be used. The cap 80, which is used to seal the opening or aperturein the lock unit 78, is removed by a simple one-quarter turn and placedon the lid 30 Where it may be held by an attached safety line 82. Thelower end of the inlet conduit 42 of the quick disconnect fluid fitting16 is now inserted through the aperture in the lock unit 78 and into thepassageway 44 of the filter element spool 34. At this point the keys 74of the quick attach and release catch 72 are aligned with the grooves 76in the lock unit 78. The fluid fitting 16 is now pressed down until thekeys 74 are seated at the bottom of the grooves after which the fittingis rotated one-quarter turn thereby locking it onto the container 12 ina fluid tight manner.

With the fluid fitting 16 now locked in place the silver containingsolution is fed into the recovery unit through the inlet port 38 andconduit 42 in the direction indicated by the arrowheads 84. The silvercontaining solution flowing from the lower end of the conduit 42 intothe open area 24 at the bottom of the container 12 where it is diffusedand permitted to flow upward through the apertures 28 into the fillerelement 14. While passing through the filler element 14 in an upwarddirection the solution will react with the metallic element causing thesilver salts contained in the solution to be deposited as a sludge inthe filler element thus leaving a substantially silver free fixingsolution. This fixing solution will be forced on through the fillerelement and will be collected in the open area 36 at the top of thecontainer 12 where it is withdrawn through the outlet conduit 56 andport 54 in the direction indicated by arrowheads 86.

As will be apparent, should any sudden pressure build-up develop in theinlet conduit 42 or outlet conduit 56, either or both of the pressurerelief valves 53 and 71 will open. This opening of, the valve or valveswill prevent any damage to the silver recovery unit 10 or the processingequipment feeding the unit.

Whenever the metallic filler element 14 need to be replaced, as willoccur when it becomes depleted with silver sludge, it is only necessarythat the quick release fitting 16 be pressed down and rotatedone-quarter turn until the keys 74 are aligned with the grooves 76 afterwhich the entire fitting is Withdrawn from the container 12. The cap 80is then replaced on the lid 30 and the container 12 with the fillerelement 14 inside is ready to be shipped to a silver processing plant.At the processing plant the remaining part of the filler element and thesilver sludge is removed and smelted or, if the container 12 has noremovable lid, the container and remaining filler element with thesilver sludge can be placed in the smelting vat thus alleviating theneed for ever removing the filler element 14.

From the foregoing it will be apparent that the silver recovery unit ofthis invention has numerous advantages over any heretofore known or usedby the silver industry. For example, the novel fluid fitting andcontainer permits a spent or saturated filler element to be replacedwith a new cartridge unit in a matter of moments without the services ofa trained technician or any special tools being required. This quickinterchange alleviates the need to either stop the photographicdeveloping process during the time required to change the silverrecovery unit or accept the loss of large quantities of silvercontaining solution as has heretofore occurred. The safety factorafforded by the pressure relief valves or bypass system is alsoaccomplished without the use of additional units on the fluid lines ashas often been required in the past. Furthermore, the fact that thecontainer serves as both the shipping and storage unit for the fillerelement, as well as the container during the silver recovery operation,is very important since it eliminates a laborious and expensive handlingoperation that was heretofore necessary when other prior known silverrecovery methods were used. The continuous wound or disc shaped, spoolcarried metallic filler element of this invention is also importantsince it is easily produced and gives superior results.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. Apparatus for recovering silver from a silvercontaining solution,comprising:

(1) means defining a container having an opening therein;

(2) core means positioned within said container, said core means havinga longitudinal passageway extending therethrough;

(3) continuous fluid permeable metallic filler means peripherallydisposed about said core means to space said core means from theinterior wall of said container, said metallic filler means being formedfrom a metal above silver in the electromotive force series; and

(4) fluid fitting means removably attached to and closing said containerfor receiving silver-containing solution from a source thereof,circulating said solution through said container so that the silver insaid solution is deposited in said metallic filler means and dischargingthe solution which the silver has been removed, said fluid fitting meanscomprising:

(a) a first fluid conduit open at one end extending into said containerthrough the opening therein and passing through the passageway in saidcore means in substantially fluid tight relationship with the wall ofsaid passageway and with the open end thereof in juxtaposition with oneend of said metallic filler means, and

(b) a second fluid conduit open on one end extending into said containerthrough the opening therein in spaced surrounding relationship With saidfirst fi-uid conduit to provide a passage for fluid flow therebetweenand with the open end thereof in juxtaposition with the other end ofsaid :rnetallic filler means.

2. Apparatus as described in claim 1 including a perforated diffusionplate positioned within said container perpendicularly to the axis ofsaid first fluid conduit and in proximity to the open end thereof touniformly direct the flow of solution within said metallic fillerelement.

3. Apparatus as described in claim 1 wherein said container is acylindrical container having an opening in one end thereof, said coremeans is positioned so that said longitudinal passageway is in alignmentwith said opening, and said first and second fluid conduits are circularpipes extending into said container through the opening therein inconcentric relationship to provide an annular passage for fluid flowtherebetween.

4. Apparatus as described in claim 1 wherein a pressure release means isincluded in said first and second fluid conduits to prevent the build-upof excessive pressure within the apparatus.

5. Apparatus as described in claim 4 wherein said pressure release meansconsists of a pressure relief valve included in each of said first andsecond fluid conduits.

6. Apparatus as described in claim 4 wherein said pressure release meansis an inverted U-shaped conduit connected between said first and secondfluid conduits and having an aperture in the top thereof for releasingany excessive pressure existing within the apparatus.

7. Apparatus as described in claim 1 wherein said metallic filler meansis steel wool.

8. Apparatus as described in claim 7 wherein said steel wool is wrappedin a number of spirals adjacent said core means.

References Cited UNITED STATES PATENTS 783,600 2/ 1905 Waterbury -109 X1,872,430 8/1932 Ericson. 2,007,615 7/1935 Ross 210-439 X 2,194,0563/1940 Quaglia 75-109 2,655,264 10/1953 Thorne 210- X 2,712,931 7/ 1955Maddock 266-22 2,758,719 8/1956 Line. 2,905,323 9/1959 Megesi 75-109 X3,043,432 7/1962 Megesi 210-439 X I. SPENCER OVERHOLSER, PrimaryExaminer.

75 R. S. ANNEAR, Assistant Examiner.

Dedication 3,369,801.-Haflan G. Hartman, Rochester, NY. SILVER RECOVERYUNIT. Patent dated Feb. 20, 1968. Dedication filed Jan. 9, 1975, by theassignee, Eastman Kodak Company. Hereby dedicates to the Public theentire remaining term of said patent.

[Oflicial Gazette March 25, 1.975.]

